Add: initrd filesystem utilities (ls, cat) + docs

docs/DEVELOPERS.md

@@ -7,6 +7,7 @@
 - Emulated booting in UEFI mode
 - Writing programs for BlankOS
 - Changing the TTY font
+- Changing the initial ramdisk content
 
 ## Getting Started
 
@@ -119,3 +120,10 @@ readelf -s -W build/fonts/YOUR_FONT_8x16.o
 Get the symbol name that ends with `_start` and replace all occurences of it in the `src/drivers/framebuffer.c` file.
 
 Then, run `make` again and the font should have changed properly.
+
+## Changing the initial ramdisk content
+
+The system loads an initial ramdisk as a simple TAR file located in `iso/boot/initrd.tar`.
+You can add, delete, or modify this file's contents by doing that in the `src/initrd` folder. Anything in that folder will be added to the initial ramdisk and will therefore be loaded into the system.
+
+The ramdisk gets loaded as a GRUB2 module.

docs/USERS.md

@@ -113,3 +113,15 @@ Makes a cow speak!
 #### `pi <terms>`
 
 Computes Pi up to a couple of digits using the Leibniz series; takes one integer argument, the number of terms of the series to compute.
+
+### Initrd utilities
+
+You can browse the (really) simple TAR filesystem with the following commands:
+
+#### `ls`
+
+Lists all files present in `initrd.tar`.
+
+#### `cat <file>`
+
+Prints file content to terminal. Filename must be specified the same way as it is outputted when using `ls`.

src/kernel/initrd.c

@@ -0,0 +1,104 @@
+// Initial TAR ramdisk kernel module 
+// Author: xamidev
+// Licensed under the Unlicense. See the repo below.
+// https://github.com/xamidev/blankos
+
+#include "../libc/stdio.h"
+#include <stdint.h>
+#include "../libc/string.h"
+#include "initrd.h"
+#include "system.h"
+
+static unsigned int octal_to_int(const char* str, size_t size)
+{
+	unsigned int result = 0;
+	while (*str && size-- > 0)
+	{
+		result = (result << 3) | (*str - '0');
+		str++;
+	}
+	return result;
+}
+
+uint32_t tar_parse_size(const char* in)
+{
+	uint32_t size = 0;
+	while (*in >= '0' && *in <= '7')
+	{
+		size = (size*8) + (*in - '0');
+		in++;
+	}
+	return size;
+}
+
+void tar_find_file(uint8_t *tar_start, const char* filename)
+{
+	uint8_t *ptr = tar_start;
+
+	while (1)
+	{
+		tar_header_t *header = (tar_header_t*)ptr;
+
+		if (header->filename[0] == '\0')
+		{
+			puts("[tar] EOF\n");
+			break;
+		}
+
+		unsigned int filesize = octal_to_int(header->size, 11);
+
+		if (strcmp(header->filename, filename) == 0)
+		{
+			printf("[tar] found file '%s', size=%u bytes\n", header->filename, filesize);
+
+			uint8_t *file_data = ptr+TAR_BLOCK_SIZE;
+			printf("[tar] content of '%s':\n", filename);
+			for (unsigned int i=0; i<filesize; i++)
+			{
+				putc(file_data[i]);
+			}
+			puts("\n");
+			return;
+		}
+
+		ptr += TAR_BLOCK_SIZE + ((filesize + TAR_BLOCK_SIZE-1) / TAR_BLOCK_SIZE) * TAR_BLOCK_SIZE;
+	}
+
+	printf("[tar] file '%s' not found\n", filename);
+}
+
+void ls_initrd(uint8_t* initrd)
+{
+	tar_header_t *header = (tar_header_t*)initrd;
+	
+	while (header->filename[0] != '\0')
+	{
+		printf("%s\n", header->filename);
+		uint32_t size = tar_parse_size(header->size);
+
+		uint32_t next_file_offset = ((size+TAR_BLOCK_SIZE-1)/TAR_BLOCK_SIZE)*TAR_BLOCK_SIZE;
+		header = (tar_header_t*)((uint8_t*)header + next_file_offset + TAR_BLOCK_SIZE);
+	}
+}
+
+void cat_initrd(uint8_t* initrd, const char* filename)
+{
+	tar_header_t *header = (tar_header_t*)initrd;
+
+	while (header->filename[0] != '\0')
+	{
+		if (strcmp(header->filename, filename) == 0)
+		{
+			uint32_t size = tar_parse_size(header->size);
+			uint8_t* file_content = (uint8_t*)header + 512;
+
+			for (uint32_t i=0; i<size; i++) putc(file_content[i]);
+			return;
+		}
+
+		uint32_t next_file_offset = ((tar_parse_size(header->size)+TAR_BLOCK_SIZE-1)/TAR_BLOCK_SIZE)*TAR_BLOCK_SIZE;
+		header = (tar_header_t*)((uint8_t*)header + next_file_offset + TAR_BLOCK_SIZE);
+	}
+
+	printf("File '%s' not found\n", filename);
+}

src/kernel/initrd.h

@@ -0,0 +1,37 @@
+// Initial TAR ramdisk kernel module header 
+// Author: xamidev
+// Licensed under the Unlicense. See the repo below.
+// https://github.com/xamidev/blankos
+
+#ifndef INITRD_H
+#define INITRD_H
+
+#define TAR_BLOCK_SIZE 512
+
+#include "system.h"
+
+typedef struct
+{
+	char filename[100];
+	char mode[8];
+	char owner[8];
+	char group[8];
+	char size[12];
+	char mtime[12];
+	char checksum[8];
+	char typeflag;
+	char linkname[100];
+	char magic[6];
+	char version[2];
+	char uname[32];
+	char gname[32];
+	char devmajor[8];
+	char devminor[8];
+	char prefix[155];
+} tar_header_t;
+
+void tar_find_file(uint8_t *tar_start, const char* filename);
+void ls_initrd(uint8_t* initrd);
+void cat_initrd(uint8_t* initrd, const char* filename);
+
+#endif

src/kernel/kmain.c

@@ -14,6 +14,7 @@
 #include "kmain.h"
 #include "multiboot2.h"
 #include "kheap.h"
+#include "initrd.h"
 
 void kmain(multiboot2_info *mb_info)
 {
@@ -89,11 +90,15 @@ void kmain(multiboot2_info *mb_info)
     }
 
     if (initrd_module) {
+	initrd_addr = initrd_module->mod_start;
+
 	uint32_t initrd_start = initrd_module->mod_start;
 	uint32_t initrd_end = initrd_module->mod_end;
 	uint32_t initrd_size = initrd_end - initrd_start;
 
 	printf("[kernel] TAR initrd module found at 0x%x, size=%u bytes\n", initrd_start, initrd_size);
+	//tar_find_file((uint8_t*)initrd_start, "./hello.txt");
+
     } else {
 	puts("[kernel] TAR initrd module not found\n");
     }

src/kernel/kmain.h

@@ -28,9 +28,10 @@ unsigned int g_multiboot_info_address;
 
 uint32_t* framebuffer;
 int scanline;
+uint32_t initrd_addr;
 
 // in characters, not pixels
 uint32_t VGA_WIDTH;
 uint32_t VGA_HEIGHT;
 
-#endif
+#endif

src/kernel/shell.c

@@ -136,6 +136,8 @@ void shell_install()
   register_command("read", program_read);
   register_command("reboot", program_reboot);
   register_command("pi", program_pi);
+  register_command("ls", program_ls);
+  register_command("cat", program_cat);
 
   for (;;)
   {

src/programs/fs.c

@@ -0,0 +1,24 @@
+// Filesystem utilities (for initrd)
+// Author: xamidev
+// Licensed under the Unlicense. See the repo below.
+// https://github.com/xamidev/blankos
+
+#include "../kernel/initrd.h"
+#include "../kernel/kmain.h"
+#include "../libc/stdio.h"
+
+void program_ls()
+{
+	ls_initrd((uint8_t*)initrd_addr);
+}
+
+// Basic cat just to read, no concatenation here
+void program_cat(int argc, char* argv[]) 
+{
+	if (argc != 2)
+	{
+		puts("Usage: cat <file>\n");
+		return;
+	}
+	cat_initrd((uint8_t*)initrd_addr, argv[1]);
+}

src/programs/misc.c

@@ -73,7 +73,7 @@ void program_uptime()
 
 void program_help()
 {
-	printf("help\tpanic\twords\tprimes\trainbow\tclear\nmath\tbf\t   uptime   echo\t  sysinfo\tconway\nrot13   morse\tcowsay   time\t  read\t   reboot\npi\n");
+	printf("help\tpanic\twords\tprimes\trainbow\tclear\nmath\tbf\t   uptime   echo\t  sysinfo\tconway\nrot13   morse\tcowsay   time\t  read\t   reboot\npi\t  ls\t   cat\n");
 }
 
 // Panic

src/programs/programs.h

@@ -13,7 +13,7 @@ void program_bf();
 void program_sysinfo();
 
 void get_cpuid();
-void get_meminfo(unsigned int multiboot_info_address);
+void get_meminfo(unsigned int multiboot_info_address); // to be fixed: cannot get full memory map (sysinfo -v)
 void program_conway();
 void program_cowsay();
 void cowsay(); // Splash screen
@@ -34,4 +34,8 @@ void program_time();
 void program_read();
 void program_reboot();
 
+// Filesystem (initrd)
+void program_ls();
+void program_cat();
+
 #endif